re PR target/49313 (Inefficient libgcc implementations for avr)

	
	PR target/49313
	* config/avr/libgcc.S (__ffshi2): Don't skip 2-word instruction.
	(__ctzsi2): Result for 0 may be undefined.
	(__ctzhi2): Result for 0 may be undefined.
	(__popcounthi2): Don't clobber r30. Use __popcounthi2_tail.
	(__popcountsi2): Ditto. And don't clobber r26.
	(__popcountdi2): Ditto. And don't clobber r27.
	* config/avr/avr.md (UNSPEC_COPYSIGN): New c_enum.
	(parityhi2): New expand.
	(paritysi2): New expand.
	(popcounthi2): New expand.
	(popcountsi2): New expand.
	(clzhi2): New expand.
	(clzsi2): New expand.
	(ctzhi2): New expand.
	(ctzsi2): New expand.
	(ffshi2): New expand.
	(ffssi2): New expand.
	(copysignsf3): New insn.
	(bswapsi2): New expand.
	(*parityhi2.libgcc): New insn.
	(*parityqihi2.libgcc): New insn.
	(*paritysihi2.libgcc): New insn.
	(*popcounthi2.libgcc): New insn.
	(*popcountsi2.libgcc): New insn.
	(*popcountqi2.libgcc): New insn.
	(*popcountqihi2.libgcc): New insn-and-split.
	(*clzhi2.libgcc): New insn.
	(*clzsihi2.libgcc): New insn.
	(*ctzhi2.libgcc): New insn.
	(*ctzsihi2.libgcc): New insn.
	(*ffshi2.libgcc): New insn.
	(*ffssihi2.libgcc): New insn.
	(*bswapsi2.libgcc): New insn.

From-SVN: r176835